An influenza A N2 neuraminidase (NA) gene was cloned at the Pst 1 site of pBR322 and completely sequenced. The resulting nucleotide sequence included the expected features of a complete copy of an influenza virion RNA. The deduced amino acid sequence of the N2 NA polypeptide was consistent with that determined for an NI NA gene sequence and suggested an amino terminal orientation for membrane insertion of the glycoprotein. To study expression of the NA gene in mammalian cells, a complete copy of the N2 NA gene was cloned in the Bam H1 site of pBR322 and then in the late region of SV40 virus. African Green Monkey kidney cells infected with this vector produced an immunoprecipitable polypeptide comparable in size to NA polypeptide produced during influenza virus infection and detectable at the cell surface by indirect immunofluorescence. Functional expression was not established. To study processing and maturation, deletion mutations were generated in separate experiments at unique restriction endonuclease sites near the carboxy terminus of the molecule. One deletion resulting in absence of the entire carboxy terminus of the molecule yielded a truncated immunoprecipitable polypeptide that was not secreted, implying that membrane anchorage occurred normally.